Building construction



May 30, 1933. IM. c. vRczvslanalJlvrT 1,912,161.

BUILDING CONSTRUCTION Filed May 28, 1930 INVENTOR. MAURICE CRQSENBLATT.

ATTORNEY.

Patented May 30, 1933 UNITED STATES PATENT OFFICE BUILDING CONSTRUCTIONApplication filed May 28,

This invention relates to building constructions, and constitutes acontinuation in part of application :li-420,668, filed January 14, 1930.

It is 4among the objects of this invention; to obviate the disadvantagesof` :previous constructions; to provide an acoustic treatment with anouter exposed stratum of material which is ornamental and pleasing;

l@ to providel as an element of an acoustic treatment a foraminous sheetas a support for an exposed finishing surface without adverse effect onits sound absorbing or acoustic value; to provide an acoustic treatl5ment for building constructions which is simple and economical toinstall; to provide a building construction of high sound absorbingvalue that may be installed by standardized labor according to theirpractices;

to provide an acoustic treatment including a layer of porous materialimposed upon a layer of foraminous material; to provide a foraminous.sheet with an external juxtaposed layer of material without preventingthe transmission of sound through the fo-u raminous sheet; to apply awoven membrane as an external coating for a foraminous sheet metal orother foraminous .or perforated material layer of an acoustic treatmentwhereby the superficial aspect of the treatment is improved,reflect-ions from the under surface of the foraminous sheet are reduced,and the sound absorbing efiiciency of the treatment is improved; toprovide a ire r proof acoustical treatment; to provide a completeceiling construction. of acoustic value; to provide an aconstictreatment effecting an over-all treatment indistin- 40. guishable from aunitary surface;I to provide an acoustic treatment combining sounddamping with sound absorbing Without appreciable cost; to provide anacoustic treatment combining high acoustic value with y v thermalinsulation; .to vprovide an acoustic treatment susceptible to ornamentalsuperfcial treatment without adverse effect on its sound absorbingeieicncy; `and many other objects and ladvantages will become more 5clear as the .description Proceeds.

1930. Serial No. 456,364.

` In the accompanying drawing:

Fig. 1 represents al fragmentary vertical section through a ceilingconstruction involving this invention.

Fig. 2 represents a fragmentary perspec- 55 tive of a foraminoussubstantially rigid sheet according to this invention on enlarged scale,showing the application of a membrane of woven material thereto, andshowing in dotted lines a hand roller which maybe used to apply paste totheunder surface of said sheet prior to the application of such membraneto prevent adhesive from entering the apertures, or which may be used'when dry to secure the attachment of the membrane to the rigid sheetwithout permitting the membrance to enter into the apertures in thesheet, in the form of depressions in the face of the membrane,

Fig. 3 represents a fragmentary perspective view partially in section ofa multiple membrane of the invention comprised of an apertured sheetwith a layer of plaster, both 'the sheet and plaster having registeringopenings to provide a highly ornamental inishing element with anenhancement of the sound transmitting qualities of the multiplemembrane,

. Fig. 3a represents a Vertical section on a iagniiied scale of thestructure disclosed in `ig. 3b represents a vertical section on amagnified scale of a modification of the multiple membrane formed of theburiedsheet material and plaster layer, i

Fig. 4 represents a fragmentary vertical section of an application ofthis invention to curved surfaces,

Fig. 5 representsa. fragmentary perspective view partially broken awaythrough an application of this invention to wooden buildings or thelike.

Fig. 6 represents a fragmentaryv vertical section through another formof the application of this invention to wooden buildings, v.

Fig. 7 repxgesents an application of this invention to the roof elementsof a wooden building and, i

Fig. 8 represents a fragmentary perspec- 10 tive view, partially brokenaway, through two abutting rigid apertured membranes with a plasterlayer extending over the two sections to provide a continuous finish,and with apertures in the plaster both in registry with apertures in therigid membrane and also over the abutting unapertured edges of themembranes, to conceal the eX- istence of a line of jointure betweensections and enhance the over-all finish of the plaster layer.

The invention relates primarily to the provision of what might bedesignated as a composite or multiple membrane of general utility ofitself in the building art, of utility of itself from an acousticstandpoint when supported in spaced relation to a surface to be treated,but particularly valuable when associated with sound absorbing materialin a building construction. To take the acoustic treatment out of therealm of the specialized makeshift supericiality and into the realm ofthe building industry by providing the treatment as an integral inbuiltpart of the building construction and in so doing to provide an exposedelement for acoustic treatments which is aesthetically pleasing andornamental, in sharp contrast to the peek-marked aspect of the ordinaryalleged acoustic treatment, and which, far from involvingsacriice ofacoustic value, enpthe contrary is characterized by an enhancement ofthat value, is a feature .of the invention.

From the sound absorbing standpoint alone it would be desirable toprovide more or less thick layers of sound absorbing material, such asfelt, (for instance, among other available materials) which is sosupported vas to be exposed directly to the action of the waves of soundenergy. With sufficient area and thickness of sound absorbing material,almost any desired degree of sound absorption could be attained.Unfortunately this cannot be the only desideratum. It is necessary toconceal the lsound absorbing element by a finishing element designed tocomport substantially with the architectural scheme. Many attempts havebeen made to do this in such manner as will not seriously aectthe soundabsorbing efficiency of the sound absorbing material, such as occurs byshielding or screening off the sound energy, but the results heretoforehave been of two general classes. of such size as to be objectionablehave had to be provided in the supposed concealing element else theywould be closed by a film of paint when that was applied as a finishingcoat, or else the'application of the coat of paint has provided areflective film of such action as to seriously interfere with thetransmission of sound energy to the absorbing material behind. In theone case a peck-marked effect accompanied by a Either holesmore or lessperceptible reduction in sound absorption is achieved; in the other ashar reduction insound absorbing efficiency 1s noted.

Referring now to Fig. 1, there is disclosed a form of buildingconstruction involvin the provision of a concrete slab, designate as 10. There will be sound absorbing material associated with this slab aswill be further described, but for the present we will consider thefinishing or ceiling element of the building construction with whichthis invention deals. The finishing element may take several forms aswill be described and may be for ceilings or other walls, but in generalit may be characterized as a composite or multiple membrane regardlessof its use. In one form there is provided in substantial parallelismwith the slab, a punctured, apertured, reticulated or foraminous sheetof rigid material 11, such as of sheet metal, but obviously capable offormation from any sufficiently rigid workable 0r worked materialincluding perforated asbestos sheets. It is contemplated for instancethat a sheet of woven wire or screening of `rather heavy gauge may beformed, then passed through suitable rollers to form a flat sheet havingits upper and lower surfaces in substantially parallel planes andobviously in this case having its greatest area of voids rather than ofsolid material. For usual purposes however fairly rigid self sustainingsheet metal will be preferred. The sheet 11 has a multiplicity ofpunctures, perforations or apertures 12, in which in one form of theinvention at least, the material of the sheet has been punched out toform a smooth surfaced sheet, the opposite faces of which aresubstantially parallel. The sheets 1l which may be of any conven`i entsize may be attached in any desired manner to some part of the buildingstructure, as for \instance by hangers 13, in Fig. 1, or to rafters orgirders 14 as shown in Figs. 5, 6, and 7 as by nails or the like.Furring members may be provided, (not shown except by their counterparts in Figs. 5, 6 and 7), which may have channels or the like toreceive the edges of the sheets. The furring members may have a cushion(not shown) to which the sheets lare fastened to give higher soundabsorbing value. Such 'furring members may be provided in using this4invention in connection with an ordinary superficial imposed acoustictreatment in place of the building construction in which it finds itslargest usefulness, and are of the usual nature for suspended ceilings.The lperforated sheets may have furring spot welded or otherwiseattached to the back before erection to stifi'en the sheet andfacilitate positioning of `it. In ,any case the sheets are attached in adesired position, with the lower surfaces of all the sheets in asubstantial plane and, preferably, with the edges of adjacent sheets inabutting relation to form a planar surface. The foraminous sheet metal,or the like, may be designated as a primary membrane. Obviously thesheet material may be used in single sheets in panels between supportingdevices such as beams or the like (not shown), but it is preferred thatthe sheets be arranged in abutting relation to form a continuous surfacemade of a plurality of sheets.

In one form of thev invention a secondary membrane, of woven fabric,such as burlap or the like, is affixed to the lower surfaces of theprimary membranes 11, as by an adhesive such as paste, glue, cement, orthe like. The object of the provision of the secondary membrane is toconceal the sheet material 11 and the apertures l2 formed in the sheetmaterial, without plugging up such apertures in any way. Where there area plurality of abutting sheets 1l, the secondarymembrane functions toblind out the lines of jointure between such sheets and thus to providean over-all finish. To

this end cement may be rolled over joints in sheets, or a tape may bepasted over joints to conceal an irregularities such as are lformed bythe astening staples or the like. The secondar membrane `may be appliedin several di erent ways, but a preferable method is to provide a rolleras indicated at 9 in dotted lines in Fig. 2, upon which adhesive isspread, then the roller is moved back and forth across the lower surfaceof the sheet material 11 depositing a thinlayer of adhesive on the solidor-V tions of the plate or sheet, but which rol ing deposits noappreciable amount of paste in any part of the apertures 12. Thesecondary membrane 15, which lis preferably long enough to cover`several sheets 11 so as to -blind out their lines of jointure, ispreferably placed under slight tension and pressed up into pastedengagement with the plate or sheet metal 11. This may be done by hand orby a suitable roller, such as 9, eX-

`erting uniform pressure on `the secondary membrane. It requires butlittle experience I to enable an ordinary Workman to apply the secondarymembrane to the vprimary apertured membrane in such a manner as tomaintain a. plane surface on the fabric secondary membrane, with suchmembrane unmarred by indentations of the membrane at points in registrywith the apertures or holes 12. Obviously, the secondary membrane may beapplied in any way that is deemed expedient although it is desirable toavoid the formation of a film of paste on the membrane in registry withthe apertures, as this forms a reflective surface effectivelyinterfering with the transmission of sound energy through the aperturesin the primary membrane. If such film is formed it may-be removedaccording to my invention by subjecting the membrane to the action of amoving stream of air, either by a vacuum devi e or by projecting acompressed air orother moving stream upon itsv surface while theadhesive is still moist enough to be dislodged from,l the pores by suchmoving airstream. The secondary membrane may be painted and decorated inany way desired to secure a desired finish, but it is undesirable topermit the formation of a film of paint on the membrane in registry withsuch apertures and to this end While the paint is still wet enough to bedislodged from between the strands of the fabric the membrane issubjected to the action of a moving stream of air of sufficient force toblow the excess paint from the fabric membrane so as to maintain theporosity of such membrane where it is in registration with the aperturesin the primary membrane.

The composite or multiple membrane may j be disposed as shown in theseveral figures, may be given a curvature, (preferabl prior to theapplication of the fabric mem rane), and provides an over-all finishwhich completely blinds out the linesl of'jointure that may existbetween edges of the sheets of apertured` material. If desired, theremay be two fabric membranes applied to the rigid backing sheet withoutappreciable reduction in sound absorbing efficiency, such for instanceas a coarse membrane initially Iimposed upon the sheet metal, and then asecondary membrane of finer mesh mounted on the first one, as shown inFig.'1, at 16. It will not usually be necessary to use two of the fabricmembranes. Y y

Of course the reticulated or porous sheet vmaterial may be applied whendesired during the building construction, but it is usually the lastelement to be applied after the introduction of the sound absorbingmaterial. For the installation of sound absorbing elements it is usuallypreferred to provide -a series of transverse supports 17, (Fig. 1.),upon which a layer or layers of 'sound absorbing material as 18, may bedraped or looped, preferably in substantially lsinusoidal form, anddisposed `between the lower surface of the slab and the upper surface ofthe skin or membrane disclosed. On the other hand, it might suffice forcertain purposes that the sheet material or primary membrane be appliedin independent strips, suitabl supported, and upon the upper surface ofywhich loose fibrous sound absorbing material may be deposited. This maybe done by using a blower to propell the loose fibrous material to thepositions needed. 'Theloose material is 'deposited as shown at 20, toany depth recglired. "If

desired both sorts of sound absor ing'mec ium may be utilized, as shownin Thus the upperlooped element may com-l prise felt, or other analagousstratified material such' as properly shaped liber boards, While thelower sound absorbing element may comprise felt, asbestos, mineral,rock, wool, or cellular refuse material or the like. If a great area ofsound absorblng material is desired it may be desirable to provide areticulated looped element, such as wire screen, or the like, hangingupon the transverse supports 17, and upon the upperA surface of whichmineral, Wool or such cellularrefuse materials as may be expedient, maybe dumped to a depth which is satisfactory. The amount may be regulatedto give any degree of acoustic absorption. In auditoriums for instanceWhere there are high furred spaces above, after the auditorium isopened, more absorbing material may be provided or absorbing materialtaken out until exactly the proper degree of absorp- -tion is presentfor perfect hearing conditions. rlhis cannot be done with any other formof treatment.

The invention contemplates a modified skin or multiple membrane, asindicated in Figs. 3, 3a, and 3b, and at the right hand side of Figs. 1,4, 5, 6, and 7. In this modification the sheet metal 21 if metal is thematerial used, and others are available of course, has a multiplicity ofapertures 22 punched or pierced and drawn or otherwise formed in thesheet, with the material drawn out forming flanges surrounding theapertures, such as in the form of burrs, as at 23. Obviously the shapeof the burrs Will vary in accordance With the nature of the punchingoperation and may vary from those which are of inverted conical offrustoconical outline, to those which are frustoconical with the base atthe outwardly flared end of the burr. For purposes of illustration, theburrs are shown in Figs. 3 and 3a as forminfr substantial continuationsof the inner surf-ace of the apertures so that they are of substantiallythe same diameter throughout, from the upper end in the plate to thelower end formed by the burr edges.

The form of burred sheet shown in Fig. 3b is preferred for certainpurposes. In this form the burrs are constricted or tapered so as to beeach of increasingly smaller diameter than the diameter of the aperturein the sheet as it approaches its end or termination. The effect of thisform of burris to provide a suitable bond' with the plaster but toarrange that the mouth of the burr, which determines the size of theaperture 'in the plaster, shall be smaller than the hole or aperture inthe sheet material. This, for utmost efficiency requires that theapertures in the sheet be closely grouped so that there are amultiplicity of the appreciably smaller openings in the surface of theplaster. The smaller plaster openings may be of such visualinsignificance as-to be substantially unnoticeable, although forming inthe aggregate a great pore or void area. This construction, when theplaster surface 1s properly applied and-tooled, cannot readily be toldfrom an ordinary plaster surface and yet has such an appreciable pore oraperture area as to be highly efficient in permittin sound energy topass through the multipe membrane. These burred holes will'in eithercase preferably be relatively small and. on closel grouped or spacedcenters. The sheets, p ates or strips of punched or pierced metal willbe applied in the same relation to the under side of the slab or to therafters or yjoists shown in the other fi res either before or after theinsertion o the Vdamping or sound absorbing material7 which, having beenonce described need not .be repeated, as the same reference charactersapply to the materials associated with either plate or compositemembrane form.

The plates, sheets or strips having been I properly placed are thencoated with a coat of plaster 24, substantially to the level of theburrs surrounding the apertures, and possibly covering same. The plaster24 may initially cover the entire surface so that no apertures arevisible, and the finish may be of any desired sort, and, temporarily atleast, there may be a small film ofy plaster lodged in the burrs andopenings in registry therewith. The plaster may then be treated whileWet or it may Wait until it has at least partially set before furthertreatment is in order.

With the plasterpkeyed or bonded to the plate by the burrs, it Will beclear that the film of plaster covering the apertures in the plate maybe. removed and form Well defined closely grouped inconspicuousapertures in the plaster surface. The removal of such lm may be done inseveral Ways. The plaster may while still moist be subjected to theaction of a moving stream of air, Whether by vacuum treatment or by astream or jet of air projected upon the surface. Or it maybe brushed,stippled, or otherwise treated with a brush, or it maybe rolled with aroller having more or less yielding points so as to break out the looseplaster, it may be treated as called for in my Patent :#1,751,249 inorder to provide a multiplicity of visually insignificant pores, eachpore that registers with the opening in' a burr being slightly enlarged,or the plaster in the burrs may be picked out from behind in any desiredmanner, assby rolling the upper surface with a device built inaccordance with the provision of burred apertures in the sheet, so thateach hole is entered to break out the film of plaster in the burr. Onthe other hand,' interesting effects may be attained by treating thesurface to break out the plaster in the burrs in accordance with adesign, as by applying a stencil or the like to the surface. The effectof the plaster to the eye of the observer is excellent, and may beenhanced in ornamental value by suitable hand tooling operations, or byimparting a rough sand cast finish. With such construction the visualeffect is, as stated, very desirable, the apertures are relativelyinsignificant and merge into the texture of the plaster to such a degreeas to require keen eye-sight to be discernible. f

If desired, the plastered apertured sheet may in turn support asecondary imposed fabric membrane as shown at in Fig. 1.

In the form of multiple membrane shown in Fig. 2 the membrane 15extending over several strips of sheet material 11, effectively blindsout the joints between adjacent or contiguous sheets. In the form ofmultiple membrane shown in Figs. 3 and 3a, the edges of the aperturedsheet material usually forming a marginof unperforated material, maybring two contiguous sheets or strips into vabutting engagement in suchmanner that .it u

might appear as an appreciable area of unperforated sheet metal betweenAperforated areas. These marginal portions may be punched or otherwisetreated to form a bond with vthe plaster if such is desirable, and thearea is plastered to the same level as the apertured or bnrred portions,then this intermediate area of plaster is rolled with rollers havingindentations or raised portions, while still moist,`in order to providea surface that simulates any other area ofv the element. Thus there willbe a substantially unbroken area of similar` superficial and visualcontour or appearance over the entire surface so treated. This will beclear from a consideration of Fig. 7 in which this is illustrated. Thetwo ends of the adjacent .sheet strips abut at line 26, with themarginal portions 27 forming an area of no apertures. This area iscovered with a llayer of plaster to the same thickness as that on theburred areas superficial appearance. Y v

Obviously the composite membrane of this invention lmay be pre-formedand attached in units if desired. It is not necessary to firstattach'the apertured sheet metal before applying the secondary membrane,although the general purposes such procedure is preferred. n

The invention involves certain improvements of importance in other typesof buildings such as homes or similar structures in which the supportingelements` are of woodV or the like..` Thus, in Fig. 5 the treatment isshown applied to ja ceiling having wooden or similarjoists, as`28. Theseas usual are arranged in parallel spaced relation, and ma ave crosssupports or rods 30, upon which sound absorbing material of any desiredsort is sup orted, preferably arranged in a longitudina 1y extendingseries of loops,

of such width as to substantially fill the distance between joists, asdesignated at 31. To the lower faces of the joists the skin devices ormultiple membranes of this invention may be directly attached, eithertype being available in the connection, as shown.

A feature of importance is the use of the invention as a combinedvibration damper and sound absorber. For this purpose with the floor ofa structure to be dealt with, and with the usual wooden joistconstruction comprised of spaced joists 32, the roll of felt or the likeis arranged transversely of the joists, arranged to pass over each joist, and to be suspended in loops therefrom, as shown at 33. Then a'sub-floor 34 is nailed to the joists compressing the felt wherel it goesover the joists, which therefore acts as an isolating support for thesub-Hoor, while the felt between joists is used as a sound absorbingelement to absorb sounds arising from below. The lower edge, or ceilingof the room below, has the rigid apertured sheet material and compositemembrane of this invention applied to the lower faces of the joists asshown.

In the construction of certain buildings at points such as the roof,(although obviously available for other points), it is desirable tocombine the sound absorbing efficiency. of the treatment ldescribedherein, with thermal insulation. To this end, as shown in Fig. 7, therafters of` the roof, as 35, form the support for strips of soundabsorbing mate rial such as 36, arranged in loops between the joists orrafters, and having a planar layer of thermal insulating material 37laid upon the upper loops of the material 36, and through which thenails attaching the sheathing 38 to the rafters 35 pass. Theundersurface of the roof may be finished with the multiple membrane ofthis invention,

.either such a sheet assembly as is shown by 11 and 15, or by the sheetand plaster assembly shown' at 22 and 24:,A or by combinations of thesheet, plaster and membrane as hown at the lower right hand corner of amaware that attempts have been made in the past to utilize a perforatedvsheet met# al strip in such relation hitherto, but in all such previousattempts the sheet metal plate has, except for a coat of paint, been theultimate exposed surface, and has been used to conceal the soundabsorbing material disposed behind such sheet and the surface of theslab or the like, to bedescribed. This has been opento certainlobjections which, as they are obviated by the invention herein, mightwell be pointed out. v Such previous efforts have necessarily beenprovided in the form of tiles or panels andthe line of jointure betweentiles has been obvious,y

and thus the provision of an over-all surface hasbeen precluded; inorder to prevent the formation of a paint film over the apertures in theplate or sheet material, they have had to be made of large area, elsethe normal film forming characteristics of the .5 paint would close themup and render the exposed surface more highly reiiective, ac-

cording toknowledge in the art prior to my invention herein; thesuperficial'aspect of the device was displeasing, having a pock- 10marked effect.

For these and other reasons the stamped metallic sheets of the past havenot been of very great commercial interest. In the instant invention,however, owing to the fact that the foraminous or reticulated sheet isto be covered as will be described, it is possible to use small or largeapertures, and as closely spaced or grouped as is desired in order tosecure the maximum of void area 2o in order in turn' to secure theutmost sound energy transmitting qualities in the sheet.

It being understood that the effort in every acoustic treatment of thistype is to provide a superficial skin, or the like, which of itself mayor may not have sound absorbtive value, so long as it has the necessaryporosity to permit the sound waves to pass through the outer skin tohave their energy absorbed behind the skin in such sound absorbingmaterial as may be provided. The sheet l1 then, has preferably amultiplicity of the apertures 12, on closely grouped or spaced centersso as to provide, preferably, that at least 50% and preferably themaximum area of the sheet is void. That is, with more hole area thansolid area.

It will be observed that the invention provides a substantially rigid,self sustaining assembly, capable of in itself supporting the soundabsorbing material, but which provides an attractive finish notheretofore obtainable from any form of foraminous assembly. It will benoted that the invention is of the utmost simplicity, that theapplication of the foraminous sheets falls within the scope ofactivities of metal lathers, while the plastering falls within the scopeof 'activities of plasterers, so that ordinary labor skilled in thosefields is adequate to make the complete installation. In every case theinstallation is ire resistant, and can easily be made completely reproofif thisiis desired.

I claim as my invention:

l. In a building construction, a surfacing element comprised of a thinself-sustaining rigid layer of non-absorbing material having inner andouter surfaces and a multiplicity of apertures extending from onesurface of the layer to the other. of such size as to admit soundenergy,^the outer surface between the apertures being a smoothcontinuous reflective surface, a thin exible porous decoratable membraneadherent to the 65 outer surface between apertures with the portions ofthe membrane in registry with the apertures in stretched condition, thewhole so arranged as to conceal the apertures and present a planarmembrane surface substantially free of surface indentations whileadmitting sound energy to the apertures.

2. In a building construction, a surfacing element comprised of a.plurality of thin .self-sustaining rigid layers of non-absorbingmaterial having inner and outer surfaces and a multiplicity of aperturesextending from one surface of the layers to the other of such size as toadmit sound energy, the outer surface between the apertures being a'smooth continuous reflective surface, the la ers being disposed withtheir outer sur aces in parallelism with adjacent layers in laterallyabutting relation, a thin fiexible porous decoratable membrane stretchedin parallelism with the outer surfaces and overlying a plurality oflayers, said membrane adherent to the surfaces between apertures andconcealing the apertures and the joint between adjacent layers, thetension on themembrane being such as to provide a planar membranesurface substantially free of indentations while admitting sound energyto the apertures.

3. A finishing element for building constructions comprising asubstantially rigid layer of material having apertures, portions of saidsheet struck up from the external surface thereof surrounding theapertures in the form of burrs, a layer of plaster imposed on theexternal face of said sheet to substantially the average level of saidburrs, said layer of plaster having apertures in registration with someof the apertures on said sheet.

4. In a building construction, a pair of joists, sound absorbingmaterial mounted between the joist-s, and a multiple membrane mounted onthe joists in spaced relation to the sound absorbing material andcomprising an apertured sheet of substantially rigid material,` and acoat of ,plaster on the apertured sheet having apertures registeringwith some of the apertures in the ri `d sheet.

5. A finishing element for buil ing constructions comprising asubstantially rigid layer of material having apertures, a layer ofplaster mounted on said rigid sheet and also provided with aperturesregistering with some of the apertures in said sheet, and a sheet oftextile membrane mounted upon said layer of plaster having oresreg:istering with the apertures in said sheet.

6. A finishing element of a building con.- struction comprising a. sheetof fairly rigid material having1 a plurality of apertures, portions ofthe s eet struck up to form burrs substantially surroundingeach-aperture on one side of the sheet, the mouth of the burr being ofsmaller averagediameter than the diameter of the aperture, and a coatingof a thickness substantially the same as the average length of the burrson the burred side of said sheet having apertures registering with themouths of some of the burrs.

7. In a building construction, a multiple membrane comprised of twosections of rigid sheet material havin each a plurality of apertures,and dispose with their edges so disposed as to form a perceptible joint,a

plaster finishing element imposed upon both sections and covering theline of the edges thereof, said finishing comprising a secondarymembrane, and having apertures in registry with some of the apertures insaid sheets, said membrane having some apertures out of registry withapertures in said sheets to effectively conceal the existence of suchjoints formed by the edges of said sections and effect an over-allfinish.

8. A finishing element for building constructions comprising asubstantially rigid plate having a surface comprised of plaster' havingapertures passing through the plate,

a sheet of textile membrane mounted on the plate and having poresregistering with the apertures in said plate.

Signed at Philadelphia, county of Philadelphia and State ofPennsylvania, this 22 day of May, 1930. A a

MAURICE C.v ROSENBLATT.

